NEW YORK, Oct 4 (Reuters) - Oil prices jumped 4 percent on T hursday as inflamed Middle East tensions stoked supply fears and U.S. gasoline futures rallied following a fire at the largest operating refinery in the United States.

Brent crude posted the biggest percentage gain since late June as news of the refinery fire at the diesel hydrotreater unit at Exxon Mobil's Baytown, Texas, refinery sent RBOB gasoline futures up more than 5 percent at times in afternoon trade.

Further support for oil came from U.S. equities gains after weekly jobless claims data suggested improvement in the labor market ahead of the monthly nonfarm payrolls report to be released on Fri day.

In the most serious cross-border escalation of the 18-month uprising in Syria, Turkey stepped up retaliatory artillery strikes on a Syrian border town after what it called "the last straw" when a mortar hit Akcakale, killing a mother, her three children and a female relative.

The market had been on edge about possible disruptions to supplies from the oil-rich region due to the standoff between the West and Tehran over Iran's nuclear program.

"You have the Middle East and the euro strong against the weaker dollar because people think Europe may yet get a handle on their debt crisis," said Phil Flynn, analyst at Price Futures Group in Chicago.

"Gasoline and heating oil are stronger because of the refinery fire."

The euro hit a two-week high against the greenback, giving a boost to dollar denominated commodities, after European Central Bank President Mario Draghi affirmed his commitment to preserve the region's monetary system and its currency.

Brent November crude rose $4.41 to settle at $112.58 a barrel, snapping three days of losses that had pushed prices to just above $108 a barrel.

The settlement left Brent back above the 200-day moving average of $112.11 and the 50-day moving average of $112.28, technical levels closely watched by chart-watching traders and analysts.

U.S. November crude gained $3.57 to settle at $91.71 a barrel, back above the 100-day moving average of $89.95 and ending a two-session string of losses.

The oil complex was led by U.S. RBOB gasoline, which shot up 14.34 cents to settle at $2.9429 a gallon, moving back above the 100-day moving average of $2.8780 and putting the 200-day moving average of $2.9696 in sight.

With U.S. product inventories tightening and the winter heating season looming, traders keenly monitored developments at Exxon's massive 560,500-barrel per day Baytown complex.

The company said Wednesday's fire had impacted production but that the problems had been contained in one processing unit which sources familiar with refinery operations said was a diesel hydrotreater.

Support also came from news that a smaller, 130,000-bpd Saratov refinery in Russia also caught fire o n T hursday.

(Additional reporting by Matthew Robinson in New York, Alice Baghdjian in London and Ramya Venugopal in Singapore; Editing by Marguerita Choy, Alden Bentley and Jim Marshall)